Locking part for joining boxes



FIG. 1 is a perspective view of a locking part for joining boxes showing my new design;

FIG. 2 is a perspective view thereof;

FIG. 3 is a top view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a right side view thereof;

FIG. 7 is a front view thereof; and,

FIG. 8 is a bottom view. 

The ornamental design for a locking part for joining boxes, as shown and described. 